The spine is formed of a column of vertebra that extends between the cranium and pelvis. The three major sections of the spine are known as the cervical, thoracic and lumbar regions. There are 7 cervical vertebrae, 12 thoracic vertebrae, and 5 lumbar vertebrae, with each of the 24 vertebrae being separated from each other by an intervertebral disc. A series of about 9 fused vertebrae extend from the lumbar region of the spine and make up the sacral and coccygeal regions of the vertebral column.
The main functions of the spine are to provide skeletal support and protect the spinal cord. Even slight disruptions to either the intervertebral discs or vertebrae can result in serious discomfort due to compression of nerve fibers either within the spinal cord or extending from the spinal cord. If a disruption to the spine becomes severe enough, damage to a nerve or part of the spinal cord may occur and can result in partial to total loss of bodily functions (e.g., walking, talking, breathing, etc.). Therefore, it is of great interest and concern to be able to treat and correct ailments of the spine.
When conservative efforts fail, treating spinal ailments very often includes a combination of spinal fusion and fixation. Generally, spinal fusion procedures involve removing some or all of an intervertebral disc, and inserting one or more intervertebral implants into the resulting disc space. Introducing the intervertebral implant serves to restore the height between adjacent vertebrae (“disc height”) and maintain the height and/or correct vertebral alignment issues until bone growth across the disc space connects the adjacent vertebral bodies. Fusions may be performed across a single level or multiple levels.
Fixation systems are often surgically implanted during a fusion procedure to help stabilize the vertebrae to be fused until the fusion is complete. Fixation systems often use a combination of rods, plates, pedicle screws, and bone hooks to attach a fixation construct to the affected vertebrae. Like the fusion, the fixation system can be implanted across a single level or across multiple levels, and typically, the fixation system is positioned to span each level to be fused. Fixations systems are designed to engage either the posterior elements (e.g. pedicle screw systems, spinous process plates) or anteriorly, the vertebral bodies (e.g. plates, anterior staple/rod systems). The configuration required for each procedure and patient varies due to the ailment being treated, the specific method of treatment (e.g. surgical approach, etc. . . . ) and the patient's specific anatomical characteristics.
A trend in the medical community is the move away from performing surgery via traditional “open” techniques in favor of minimally invasive or minimal access techniques. Open surgical techniques are generally undesirable in that they typically require large incisions and high amounts of tissue displacement to gain access to the surgical target site, which produces concomitantly high amounts of pain, lengthened hospitalization (increasing health care costs), and high morbidity in the patient population. Less-invasive surgical techniques (including so-called “minimal access” and “minimally invasive” techniques) are gaining favor due to the fact that they involve accessing the surgical target site via incisions of substantially smaller size with greatly reduced tissue displacement requirements. This, in turn, reduces the pain, morbidity and cost associated with such procedures. For example, a minimally invasive lateral (from the patients side) approach to access the disc for fusion has been developed over the last decade and demonstrated great success in reducing patient morbidity, shortening the length of hospitalization, and decreasing recovery time when employed.
Minimally invasive posterior pedicle based fixation systems are also now well known in the art and can be used in conjunction with the lateral based access for fusion when multiple levels are involved. However, this can be disadvantageous in that it generally involves repositioning the patient in between the fusion procedure and the fixation procedure. On the other hand, the availability of minimally invasive fixation systems for fixing to the anterior column is generally limited to single level procedures. Accordingly, there is a need for minimally invasive fixation systems designed to engage the anterior column across multiple levels, particularly in conjunction with a lateral access fusion procedure.
The devices and methods described in the present application address these needs.